The use of Lewis acids to catalyze cationic polymerization of various organic compositions is generally known. Incorporation of compounds, which release a Lewis acid upon photolytic degradation, into photopolymerizable compositions has also been described in the literature. U.S. Pat. Nos. 3,708,296, 3,794,576, 3,816,279, and 3,205,157 disclose the use of aromatic diazonium salts; U.S. Pat. Nos. 4,150,988, 4,069,055, and 4,069,056 disclose the use of Group VA onium salts; U.S. Pat. No. 4,069,054 discloses the use of sulfonium salts as photoinitiators; and Crivello, in Chemtech, Oct., 1980, pp. 624-628, discloses the use of diaryliodonium salts. Disadvantages of certain known photopolymerizable compositions employing various "onium", diazonium and sulfonium salts are their thermal instability and instability in a dark environment.
Certain sulfonic acid esters of N-hydroxyamides and -imides are known. U.S. Pat. Nos. 4,111,926 and 4,066,636 disclose the use of N-aryl- and N-alkylsulfonyloxyimides and N-aryl- and N-alkylsulfonyloxybenztriazoles as hardening agents for gelatin. U.S. Pat. No. 4,012,366 discloses polymers which contain hydroxamic acid-O-sulfonyl groups in the side chains; these polymers are useful for the manufacture of moldings, coatings and adhesives. Fahmy, et al., in Bull. Chem. Soc. Jpn., 50, 2678-2681 (1977) and 51, 2148-2152 (1978), describe selected chemical reactions of N-(arylsulfonyloxy)phthalimides and the numerous reaction products obtained. Cadogan, et al., J. Chem. Soc. Perkin I, 1069-1071 (1975), describe the photolysis of N-tosyloxyphthalimide in the presence of aromatic compounds to give N-arylphthalimides, and p-toluenesulfonic acid as a by-product.
An object of this invention is to provide a photopolymerizable composition which is easy and inexpensive to prepare, highly stable under storage conditions, and heat resistant.